Turntable



23, 1930. T. w. MUNDT 1,786,258

TURNTABLE Filed April 22, 1929 INVEN T'd/i Patented Dec. 23, 1930 1 UNITED STATES-PATENT OFFICE 'rnnononus WILLEM MUNDT, or BILTI-IOVEN, NETHERLANDS TURNTABLE Application filed April 22, 1929, SerialNo. 357,300, and iii Germany June 16, 1927.

Owing to the constant increase in the size and weight of locomotives, the old method of construction of turntables, in which the main girders are supported only in the middle, has been abandoned and new" methods of constructionhave been introduced; i

The new constructional forms, of which those with subdivided and those with continuous main girders have'been more generl0 ally adopted, do away with the recognized faults of the oldconstructional forms (bumping when the wheels of the leading axle run on to the turntable, the necessity of balancing the locomotive as accurately as'possib'le before the turntable can be turned, high main "girders and a correspondingly deep pit, and

so on), by the wheels at the girder ends restvin'g on the race and taking up a portion ofthe load. v

The turntables with subdivided main girders, however, in mostcasesdo not turn with the same ease as the older constructions.

They have the further disadvantage that they are relatively complicated, owing to the i pivotal connection of the two halves of the main girders, while there is difiiculty in making them rigid in the horizontal direction without the provision of special means, which particularly in 3 turntables of large'diameter.

may easily cause troublemore In the turntables with continuous main - girders as at present -made, the, cross-section of the main girders 1s designedin accordance- 'Wlllll the greatest bendmgmomendthe main girders having a constant momentlof inertia over their'entire length, or the main girders f Consequently, turntables wlth contlnuous are tapered towards the ends. In order that the turntable shall move easily, it is necessary that the greater part ofthe-load'shall rest on the centre support, for which purpose thissupport should be placed as high as pos- .sible with-respect to the peripheral supports.

7 In order further that the turntable shall turn as easily as possible, with thedesired position of the rails in a horizontalplane, the V centre support must thereforebe placed so highrthat the main girders may be designed as continuous straight girders restmg on vp p points'of support of equal height and equiequidistant from one another.

eration takes too much time.

if the girders have a constant moment of inertia or if they be tapered towards the ends, the end of theunloaded arm will tilt upwards,

when the turntable is loaded on one side by a heavy locomotive, independently of whether the moment of inertia is great or small.

Hence it was necessary in turntables with continuous mam girders to place the centre support so much lower than the peripheral supports that withthe greatest one-sided load 1 to be expected the end of the unloaded arm would not tilt upwards; In view of the inequalities in the height of'the roller race, which are unavoidable in laying the race and during the operation'of the turntable, the

centre support must be placed still lower than would be necessary theoretically. This not only sacrifices the easy running of the turntable, but also increases the maximum bendingmoment so that the cross section of the In ordernot further to endanger the easy running ofthe turntable, the centre support is-i'n some cases placed so low that with the greatest inequality in the height of the race to beexpected in ordinary practice, the end that'is unloaded shall barely avoid tilting up, when the turntable is loaded on one side.

This, however, causes the adhesive pressure main girders are almost all drivenat both ends, which is complicated and uneconomical.

- l/Vhere, however, a drive on ones ide only has been provided, it is impossible to turn the turntable, when it is loaded'only on theiside lying opposite the drive, or at least it becomes sodifficult in view of the necessity. of still i further lowering the centre support that ;-.where the turntableis. driven'by hand the op iWhen a continuous girder resting on three side and its unloaded end tilts up, this tilting may be prevented by the provision of reinforcements of the cross-section externally of the centre support.

The object of the invention is to apply this principle to the design of turntables, so that all the disadvantages of the older system are done away with, a one-sided drive will sufiice and easy running is ensured.

T he cross-section of the continuous girders on three points of support of equal height is determined in accordance with the greatest negative bending moment occurring above the centre support, while, for taking up the greater positive bending moment, the cross-section is strengthened externally of the centre support, which may be effected in the simplest manner, for instance by attaching plates or, in the case of riveted girders (if the booms are to remain unaltered), by increasing the height of the web.

In most cases an increase in the strength of the cross-section, in order that the greater positive bending moment may be taken up, will be sufficient to prevent the unloaded end from tilting up when the supports are of equal height, and, the turntable is loaded on one side, thereby making it possible to adopt a one-sided drive.

Should the possible one-sided load be so great that the frictional or adhesion pressure between the drive wheels and the track is insufficient for a one-sided drive, the frictional or adhesion pressure can be made sufficient by strengthening the cross-section externally of the centre support or by placing the centre support somewhat lower.

The adoption of the construction according to the present invention enables the material to be distributed in the most favourable manner. Furthermore, as the girders are less rigid in the vertical direction than those of the older constructional forms with continuous main girders, the construction adapts itself well to the unavoidable inequalities of the race. As compared with turntables of a known kind having subdivided main girders, the construction according to the present invention is simpler and cheaper, as no linked joint is required. In addition to this, whatever the loading conditions, the total wheel pressure is considerably lower, so that the turntable will turn far more readily. As compared with the older turntables with continuous girders, the new construction has this advantage that, whatever the loading conditions, a one-sided drive on one side of the centre line of the track will suffice and that the distribution of material in the main girders is a logical one, so that the construction adapts itself more readily to any changes in the relative height of the three supports.

A constructional example of the invention is illustrated in the accompanying drawing,

' in which Fig. l is a diagrammatic representation and Fig. 2 a cross-section through the centre support.

In Fig. 1 of the drawing T is one of the main girders which extends unbroken over the sections or radial fields 1 (measured f om the center of the end bearings to the center support). The main girder is provided out side the centre support, in the fields 1 up to the points of Zero moment, over a length (L with reinforcing plates Z), in order that the greatest bending moment may be taken up and so that for all loads, the frictional or gripping pressure Will be sufficient for a mo tor drive at one girder end and to one side of the centre line of the track. According to Fig. 2 the two main girders T, which are connected by transverse bracing, rest on the annular upper part or cap 0 of the king post, from which a guiding ring d or apron extends into the lower part or base 6. The upper part or cap 0 is journalled by means of a ball race bearing f on the lower part or base (1. The guiding ring or apron d transmits the horizontally acting forces from the upper part or cap through a ball or roller bearing g to a centering spindle h which is rigidly fixed to the lower part or base butdoes not bear any weight.

The height of the centre support 0 can be adjusted in any suitable manner, for instance by introducing or removing gaskets or packing pieces.

Each end of the main girder is supported by a pair of head bearings Which are provided with rollers. The turntable may be driven by means of a motor or by hand, at one end of the girder only and to one side of the centre line of the track.

\Vhat I claim is:

1. In a turntable, a pair of continuous girders of substantially uniform cross-section suitably interconnected, central and end supports, reinforcing plates for said girders extending from said end supports short of the center support in order to provide rigidity of the griders against bending forces for the entire length of said plates, while permitting bending between the inner ends of said plates.

2. A turntable comprising suitably interconnected main girders of substantially uniform cross section. end supports for the girders and a center support therefor, reinforc ing elements for the girders positioned in a section thereof where bending stresses are greatest and extending to points of zero moment, thereby permitting bending of the structure between said points thus insuring sufficient tractive pressure at the end sup ports for operating the turntable from either end.

3. In a turntable constructed for obtaining moments of inertia of different magnitude in the portions thereof situated on either side of a center support; said turnable having continuous main girders resting on three points of support and forming a structure of un- Weakened cross-section, reinforcing plates 1 extending inwardly from the outer supports i to within a certain distance of the center support thereby stiffening the structure except between the inner ends of said reinforcingplates, thus permitting sagging of the ends of the structure over said end supports thereby permitting the turntable to'be driven from i one end thereof.

In testimony whereof I afix my signature. THEODORUS WILLEM MUNDT. 

